The present invention generally relates to a magnetic disk apparatus employed in a computer, an information processing apparatus, and so on. More specifically, the present invention is directed to a structure of a magnetic disk apparatus with employment of an electric wiring capable of satisfying an electric condition under which high frequency recording higher than or equal to 200 MHz can be realized in this magnetic disk apparatus.
As storage apparatuses of information processing appliances, semiconductor memories and magnetic member memories are mainly employed. In view of access time, semiconductor memories are employed as internal storage apparatuses, whereas in view of large memory capacities and non-volatile characteristics, magnetic member memories are employed as external storage apparatuses. Nowadays, magnetic disks and magnetic tapes are major materials of such magnetic member memories. As recording media employed in these magnetic disks/tapes, magnetic thin films are formed on either substrates or tapes.
Magnetic head recording (writing) elements having electromagnetic converting effects are used so as to write magnetic information on these recording media. Also, to reproduce (read) magnetic information, magnetic head reproducing elements are employed which may utilize the magneto resistive phenomenon, the giant magnetoresistive phenomenon, or the electromagnetic inductance phenomenon. These functional element units are provided on input/output parts called as magnetic heads.
Among these magnetic recording apparatuses, the present invention relates to a structure of a high frequency recording magnetic disk apparatus. More specifically, the present invention directs to an electric wiring itself of a magnetic head, and also a structure of a magnetic disk apparatus arranged by containing this electric circuit, and a magnetic head recording element unit, by which high frequency recording operation can be realized.
As to a major trend in high-performance magnetic recording aspects, these are one trend of a high recording density technique, and also another trend of a high frequency technique. This high recording density technique is described in, for example, Japanese magazine NIKKEI ELECTRONICS titled “Recording density by MR head available at 5 G bits/(inch)2” issued on Apr. 6, 1998, pages 155 to 165. On the other hand, the high frequency technique is described in, for example, Japanese Electronic Information Communication Institute Technical Research Report “JIKI KIROKU” published on Oct. 15, 1998,pages 7 to 12. It should be understood that the present invention is directed to a novel technique as to the latter-mentioned high frequency technique.
In the conventional magnetic storage apparatuses, frequencies used during recording operations and reproducing operations never exceed 100 MHz. However, in future, in high density magnetic recording apparatuses, data transfer performance achieved in these high density magnetic recording apparatuses must be increased higher than or equal to 50 MB/S, since a large amount of data should be input/output within a short time period. This data transfer performance of 50 MB/S defined in such a magnetic recording apparatus implies that a frequency range is increased higher than or equal to 200 MHz (50×8/2 Hz).
Within such a range that a recording frequency does not exceed 100 MHz, a twisted line is employed so as to electrically couple a magnetic head to an IC for controlling recording/reproducing operation. However, the twisted line owns such a problem that since this twisted line owns a large inductance component, a high frequency signal required for performing a high-speed recording operation can be hardly transmitted.
To solve this problem, for example, the suspension referred to as a “line-integral type suspension” is employed. This suspension is described in Japanese magazine NIKKEI ELECTRONICS issued on Apr. 6, 1998, page 168. In this suspension, the wiring lines used to supply the signals and the electric power are directly formed on the suspension. Since this suspension member is formed by way of the photo-etching manner, both the width between the wiring lines and the interval between two wiring lines can be made shorter than or equal to 30 μm. As a result, the inductances of the wiring lines can be suppressed smaller than or equal to 50 nH. Because of this effect the recording operation higher than or equal to 200 MHz may be realized in the magnetic recording apparatus with employment of the line-integral type suspension structure.
However, the wiring line is actually formed and is actually coupled to this wiring line. It could be revealed that a desirable high frequency recording operation could not be carried out in this actual case. This reason may be caused by the wavelengths of the high frequency components contained in the recording current. Therefore, in order to solve this problem, it is conceivable that the length of the electric wiring line should be shortened.
FIG. 1 shows such an example of an improvement in the line-integral type suspension so as to solve the above-described problem. The read/write IC2 is provided on the suspension 3 in such a way that this read/write IC2 is approached to the magnetic head 1. In this drawing, reference numeral 4 is an electric wiring for supplying a signal and electric power, reference numeral 5 denotes an arm, and reference numeral 6 indicates a boss used to mount the arm. This conventional technique is referred to as a “Chip on Suspension” which is reported from, for example, Japanese Applied Magnetic Institute, 22nd Lecture held in 1998.
The technique for providing the read/write IC on the suspension located near the magnetic head so as to shorten the length of the electric wiring may be obvious from the above-described technical documents. When the read/write IC is mounted on such a member having a poor heat radiation characteristic, extension and/or distortion may occur due to heat, which may cause the performance of the magnetic disk apparatus to be deteriorated. Furthermore, there is another problem that mass is increased and a total number of electric wirings is increased, since the read/write IC is mounted on the mechanical movable unit. To solve these problems, newly considered solutions are necessarily required, but these solutions could increase the cost up aspect of the magnetic disk apparatus.
Also, one technical idea capable of uniforming impedances of transmission paths has been proposed in PCT Laid-open Publication No. WO96/42080. Even when such a proposed technical idea is employed, it is practically difficult to realize the high frequency recording operation. This technical propose may prevent the reflections occurred in the signal lines by uniforming the impedances of the transmission path, namely smoothing the impedance changes.
However, even when no reflection condition is made in the electric wiring by applying the above-explained technical method, if the impedance of the magnetic head cannot be matched with the impedance between the electric wiring, then the maximum reflection may occur at this mismatching portion, so that the electric length cannot be made long.